Sensitivity to Ignition

Explosives are generally characterized by five features (1) chemical stability, (2) sensitivity to ignition, (3) sensitivity to detonation, (4) velocity of detonation, and (5) explosive strength. These characteristics can have quantitative values with statistical variations which must meet stringent requirements, especially for military use. However, the occurrence of an unexpected explosion or dud may be statistically predictable when thousands or millions of events have been tried. Perfect reliability is something which can seldom be achieved. 

The chemical stability of an explosive is determined by its ability to maintain its reactive characteristics and to remain chemically unchanged while stored or aged under specific conditions. 

extreme temperatures of 30°C or +45°C often encountered during military operations can destabilize the materials of an explosive. Chemical instability may thus be due to the nonexplosive degradation or decomposition of the explosive substance with the result that the reliability and strength is decreased. 

Explosive solids can be detonated by heat, mechanical impact, friction, or electrical spark or discharge. The sensitivity of an explosive is the effect of the stimulus on its spontaneous detonation  

Black power KNO3, 15 C, 10 S 1.2 310 0.4 2.8 280 60 Cheap, smoky, sensitive 

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Sensitivity to Ignition by Shock Wave. When initiated with Melinite (70% PA, 30% NC), it was found to have a shock wave sensy similar to PETN (Ref 51)... 

The low-melting sohd of limited thermal stability (max. safe storage temperature 20°C, self-heating decomposition detected above 30°C) will explode on heavy impact (150 kg cm), but is of low sensitivity to ignition. However, 3 cases of spontaneous decomposition in storage or transportation have been noted. 

Zirconium particles in air are sensitive to ignition by static electricity. This sensitivity increases with decreasing particle size. When Zr particles are heated in air, reaction with oxygen occurs at their surface. This reaction proceeds very violently to produce high-temperature zirconium oxide. A large number of bright light streams are emitted from the particles when they come asunder. The reaction process is represented by... 

Note These mixtures are very sensitive to ignition and can be quite dangerous to prepare. They should only be mixed by trained personnel using adequate proteetion. 

Large flakes, called "flitter" aluminum, are widely used by the fireworks industry to produce bright white sparks. A special "pyro" grade of aluminum is also available from some suppliers. This is a dark gray powder consisting of small particle sizes and high surface area and it is extremely reactive. It is used to produce explosive mixtures for fireworks, and combinations of oxidizers with this "pyro" aluminum should only be prepared by skilled personnel, and only made in small batches. Their explosive power can be substantial, and they can be quite sensitive to ignition. 

Another important factor is the thermal stability and heat of decomposition of the oxidizer. Potassium chlorate mixtures tend to be much more sensitive to ignition than potassium nitrate compositions, due to the exothermic nature of the decomposition of KCIO 3. Mixtures containing very stable oxidizers - such as ferric oxide (Fe 2O 3) and lead chromate (PbCrO 4) - can be quite difficult to ignite, and a more-sensitive composition frequently has to be used in conjunction with these materials to effect ignition. 

Another type of substance, which is less sensitive than primaries, is the class called propellants. They are explosive but formulated with different intention than HE s. Their function is to burn in a controllable fashion and, ideally, not to detonate under any circumstance. An important property of propellants is their sensitivity to ignition, which can be determined by subjecting them to sparks or flames... 

Sensitiveness to Ignition. The same tests are applied as given under Ignition Tests in this Vol. These include Fuse Test, Red Hot Iron Basin Test, and Red Hot Iron Test... 

Epreuve de la sensibilite a Tin flam matron (Sensitivity to Ignition Test). See Ref 24, p E110-R... 

With regard to their sensitiveness to ignition by light, the azides of monovalent metals may be ranged as follows ... 

Furthermore, melt flow and dripping are sensitive to ignition and burning from the top (LOI) or from the bottom (UL 94 V-classifications)34 as well as to a horizontal (UL 94 HB-classifications) or vertical (LOI, UL 94 V-classifications) specimen position during testing. Both melt flow and... 

Combustion en tas conique (Combustion in a Conical Pile), also called Epreuve de sensi-bilite a Tinflammation ou Aptitude a I inflam-mation [Sensitivity to Ignition (or Inflammation) Test]. The purpose of this test is to ascertain the ease of ignition (inflammation) of an expl or a proplnt in air. This is important from the point of view of safety in handling... 

Is the sensitivity to ignition by these sources known for all process materials ... 

Process Description Different energetic materials provide propulsive or explosive functions in rocket motors, munitions, and similar devices. These materials are made of different chemicals and have different characteristics of solubility, sensitivity to ignition, bum rate, and energy content. The potential for reuse varies widely depending on the physical form, chemical content, and reactive characteristics of the materials. 

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